Re: Problem with Checkboxes

So in the top frame of the stack you can see that the error is #value:
being called on nil. If you look at the second frame, you can see that
#value is being called on the instance variable 'callback', so clearly
that must be nil. And sure enough, if you look at your rendering code,
you have not set a callback for your checkboxes (if you don't set a
callback, you won't get the value submitted by the user).

If you add a call to #callback: when rendering your checkbox the
problem should go away. That said, obviously the framework should
handle the case of no callback more gracefully. I created the
following issue: http://code.google.com/p/seaside/issues/detail?id=106

Welcome to Seaside,

Julian

On Sun, Jul 20, 2008 at 7:46 AM, Felix Dorner <felix_do <at> web.de> wrote:
> Hey,
>
> first, I am a Squeak/Smalltalk newcomer, so please forgive me if I make an
> obvious error. I also give as much detail as I can and would greatly
> appreciate general comments.
>
> I am trying to write a small survey application, for that I created a class
> WASurvey:
>
> WAComponent subclass: #WASurvey
>   instanceVariableNames: 'survey questionsPerPage currentPage'
>   classVariableNames: ''
>   poolDictionaries: ''
>   category: 'questionaire'
>
> survey is a list of questions, questionsPerPage/currentPage should be
> obvious.
>
> The component is rendered like that:
>
> renderContentOn: html
>   | first last |
>   first := currentPage - 1 * questionsPerPage + 1.
>   last := first + questionsPerPage - 1.
>   html heading: survey title.
>   html text: currentPage; text: '/'; text: self pageCount.
>   html form: [
>       survey questions from:first to:last do: [ :question | question
> renderContentOn: html ].
>       html submitButton text: 'Previous Page';
>                             callback: [ currentPage := currentPage - 1 ];
>                             disabled: currentPage = 1.
>       html submitButton text: 'Next Page';
>                             callback: [ currentPage := currentPage + 1 ];
>                             disabled: currentPage = self pageCount.
>   ]
>
> Now I created several Question classes that implement renderContentOn:
> aCanvas
>
> MultiChoiceQuestion>>renderContentOn: html
> super renderContentOn: html.
>   answers doWithIndex: [ :answer :index |
>                                  | current |
>                                  current := html checkbox value: (values
> includes: index).
>                                  html text: answer.
>                            ]
>
> SingleChoice>>renderContentOn: html
> super renderContentOn: html.
>   html radioGroup: [ :group |
>       answers doWithIndex: [ :e :index |
>                                    | current |
>                                    current := group radioButton.
>                                    value = index ifTrue: [ current beChecked
> ].
>                                    html text: e ]
>   ]
>
>
> I currently get a MessageNotUnderstood error that seems to be related to the
> Checkbox components in MultiChoice questions. My problem is, that the
> StackTrace is very deep, and only shows Seaside internals. What would now be
> the general approach to trace down that issue?
>
> Thanks for your help,
>
> Felix
>
> Here is the top of the Stack Trace:
>
>  1.
>
>     thisContext
>     <http://127.0.0.1:8080/seaside/survey?_s=TGzVOKjnplpRtUnu&_k=VXYqwquh&4>
>         UndefinedObject(Object)>>doesNotUnderstand: #value:
>     self
>     <http://127.0.0.1:8080/seaside/survey?_s=TGzVOKjnplpRtUnu&_k=VXYqwquh&5>
>         nil
>     aMessage
>     <http://127.0.0.1:8080/seaside/survey?_s=TGzVOKjnplpRtUnu&_k=VXYqwquh&6>
>         value: nil
>
>  2.
>
>     thisContext
>     <http://127.0.0.1:8080/seaside/survey?_s=TGzVOKjnplpRtUnu&_k=VXYqwquh&7>
>         [] in WACheckboxTag>>after {[callback value: value. value :=
>         false]}
>     self
>     <http://127.0.0.1:8080/seaside/survey?_s=TGzVOKjnplpRtUnu&_k=VXYqwquh&8>
>         a WACheckboxTag
>
>  3.
>
>     thisContext
>     <http://127.0.0.1:8080/seaside/survey?_s=TGzVOKjnplpRtUnu&_k=VXYqwquh&9>
>         BlockContext>>valueWithPossibleArgument:
>     self
>
> <http://127.0.0.1:8080/seaside/survey?_s=TGzVOKjnplpRtUnu&_k=VXYqwquh&10>
>         [] in WACheckboxTag>>after {[callback value: value. value :=
>         false]}
>     anArg
>
> <http://127.0.0.1:8080/seaside/survey?_s=TGzVOKjnplpRtUnu&_k=VXYqwquh&11>
>         ''
>
>  4.
>
>     thisContext
>
> <http://127.0.0.1:8080/seaside/survey?_s=TGzVOKjnplpRtUnu&_k=VXYqwquh&12>
>         WAValueCallback>>evaluateWithArgument:
>     self
>
> <http://127.0.0.1:8080/seaside/survey?_s=TGzVOKjnplpRtUnu&_k=VXYqwquh&13>
>         a WAValueCallback
>     anObject
>
> <http://127.0.0.1:8080/seaside/survey?_s=TGzVOKjnplpRtUnu&_k=VXYqwquh&14>
>         ''
>
>  5.
>
>     thisContext
>
> <http://127.0.0.1:8080/seaside/survey?_s=TGzVOKjnplpRtUnu&_k=VXYqwquh&15>
>         WAValueCallback(WACallback)>>evaluateWithField:
>     self
>
> <http://127.0.0.1:8080/seaside/survey?_s=TGzVOKjnplpRtUnu&_k=VXYqwquh&16>
>         a WAValueCallback
>     anObject
>
> <http://127.0.0.1:8080/seaside/survey?_s=TGzVOKjnplpRtUnu&_k=VXYqwquh&17>
>         ''
>
>
> _______________________________________________
> seaside mailing list
> seaside <at> lists.squeakfoundation.org
> http://lists.squeakfoundation.org/cgi-bin/mailman/listinfo/seaside
>